Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Method for irradiating platelet concentrates in flexible containers with
ultraviolet
light
The subject matter of the invention is a method for inactivating pathogens
such as bacteria
and viruses and/or leucocytes in platelet concentrates (thrombocyte
concentrates, PCs) by
irradiation with ultraviolet light.
It is known that the therapeutic application of blood preparations carries the
risk that the
recipients of the blood preparation are infected with viruses and bacteria.
The viruses
hepatitis B (HBV) and hepatitis C (HCV) and the Aids pathogens HIV 1 and HIV 2
are
named by way of example. The risk always exists when, during the production of
the
preparation, no steps are taken to inactivate or eliminate the said pathogens.
Ultraviolet (UV) light is differentiated according to wavelength. In the
context of this
application, the following definition is applied: UVA: less than 400 to 320
nm, UVB: less
than 320 to 280 nm and UVC less than 280 to 200 nm. It is known that by
irradiation with
short-wave ultraviolet (UV) light, i.e. in the wave length range below
approximately 320
nm (UVB and UVC), viruses and also bacteria can be inactivated, for instance
in blood
plasma or in cellular blood preparations. Above 320 nm, the energy of the
radiation is too
low to inactivate microorganisms and viruses. Compared with chemical,
photochemical
and photodynamic methods of pathogen inactivation, mere irradiation with UV
light
essentially has the advantage of being effective on its own and not requiring
the addition of
reactive chemicals or photoactive substances.
Such additives or their split products or photo products frequently require
subsequent
removal, because they are toxic or mutagenic. In addition, they can cause the
formation of
neoantigenic structures in the treated preparation when they bind to plasma
proteins and
cell surfaces. Generally, such additives are not able to be removed
completely; at least,
their removal requires additional effort. Such additional working steps can,
moreover,
impair the quality of the sterilised preparations. UVC is the most effective
for direct
pathogen inactivation. However, it has the disadvantage that it only
penetrates protein-
containing solutions such as blood plasma or turbid suspensions (e.g. PCs) up
to a very
small penetration depth.
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UVC was used during the Second World War and also shortly thereafter to
sterilise blood
plasma and albumin solutions, especially in order to inactivate hepatitis
viruses. At that
time, one proceeded so that the solution was directed in a through-flow
apparatus as a thin
film past a UVC light source. The method proved to be not sufficiently
reliable and was
abandoned (Kaltenbach NR, Cornelius PA, Negus D, et al. Inactivation of
viruses by
ultraviolet light. Curr Stud Hematol Blood Tranfus 1989, 56,70-82).
In the present day, methods are used which have been further developed,
operating
according to the same principle, in order to sterilise therapeutic plasma
protein
preparations. In all cases the concern was or is with treating larger volumes,
i.e. plasma
pools or protein solutions up to several hundred litres and even more (Hart H,
Reid K, Hart
W. Inactivation of viruses during ultraviolet light treatment of human
intravenous
immunoglobulin and albumin. Vox Sang 1993;64(2):82-8, and Chin S, Williams B,
Gottlieb P, et al. Virucidal short wavelength ultraviolet light treatment of
plasma and factor
VIII concentrate: protection of proteins by antioxidants; Blood
1995;86(11):4331-6).
For sterilising a plurality of individual units of PCs, which have been
obtained from blood
donations or by mechanical apheresis ¨ with a volume of at most up to several
hundred ml
¨ the aforementioned through-flow apparatus are not suitable. However, this is
in fact
necessary in the daily practice of a blood bank.
UVB is likewise microbiocidal and virucidal, although not to the same extent
as UVC. It
penetrates protein-containing solutions and turbid suspensions somewhat better
than UVC,
but its penetration depth, e.g. in plasma or PCs, can also only be established
in the range of
a few millimetres. Irradiation with UVB was tested, in order to inactivate T-
lymphocytes
in PCs, which are considerably more UV-sensitive than viruses or bacteria.
Hereby, an
allo-immunisation against exogenous HLA antigens in the recipients of the
preparations is
to be prevented, which can cause the recipients to become refractory against
further
transfusions of PCs (Andreu G, Boccaccio C, Lecrubier C, et al. Ultraviolet
irradiation of
platelet concentrates: feasibility in transfusion practice. Transfusion
1990;30(5):401-6 and
Pamphilon DH. The rationale and use of platelet concentrates irradiated with
ultraviolet-B
light. Transfus Med Rev 1999;13(4):323-33).
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In fact, the method did not win through, because the leucocyte filtration,
which was
developed at almost the same time, constitutes an alternative which is
similarly effective
but is more favourable from the point of view of cost and effort (Leukocyte
reduction and
ultraviolet B irradiation of platelets to prevent alloimmunization and
refractoriness to
platelet transfusions. The Trial to Reduce Alloimmunization to Platelets Study
Group. N
Engl J Med 1997; 337(26):1861-9;).
It was likewise described that viruses in platelet suspensions can be
inactivated by
irradiation with monochromatic UVB light (wavelength 308 nm). An excimer laser
was
used here; the test volume was a few ml (Prodouz KN, Fratantoni JC, Boone EJ,
Bonner
RF. Use of laser-UV for inactivation of virus in blood products. Blood
1987;70(2):589-92).
Clearly, one did not depart beyond this benchmark. In fact, no method is known
from the
literature by which viruses or bacteria in complete PCs can be decontaminated
exclusively
by irradiation with UV light (i.e. UVB or UVC).
PCs are obtained by mechanical thrombapheresis from individual donors or else
are
isolated from blood donations, with the platelets from several blood donations
(generally
4-6) being pooled. The volume of the PC which is able to be obtained
accordingly
generally lies between approximately 200 and 350 ml. However, PCs are also
produced
from individual blood donations, the volume of which is correspondingly
smaller (between
approximately 40 and 80 m1). Both in pool PCs and also in apheresis PCs, the
platelets are
either suspended in blood plasma or in special storage media with a residual
plasma
content of approximately 30 to 40 Ã1/0. The PCs are stored in flat gas-
permeable plastic bags
at 20-24 C.
It would be desirable to sterilise PCs in such bags with UV light. Indeed, the
problem
which has been mentioned exists here, namely that the preparations are almost
impenetrable by UV light. This is to be clarified by the following calculation
example: if
UVB is provided for sterilisation and one assumes a PC volume of approximately
300 ml,
in addition a penetration depth of the UVB radiation of lmm and exposure of
both sides of
the bag, a suitable exposure bag would have to have a surface of at least 1500
cm2.
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It appears to be difficult, if not precluded, to routinely process larger
quantities of bags
having such dimensions. The problem becomes even significantly greater if,
instead of
with UVB, one wishes to sterilise the PCs with UVC, because its penetration
depth is
much less.
Certain exemplary embodiments provide a method for inactivating pathogens,
leucocytes
or both in platelet concentrates (PCs) comprising the steps of: providing PCs
obtained from
donor blood, by mechanical apheresis or both, in which the PCs consist of a
plurality of
units which are able to be handled individually and stored separately, and the
PC units are
each placed in flexible, UV-penetrable flat exposure bags, exposing the PCs to
irradiation
with ultraviolet (UV) light, wherein the exposure bags are filled to less than
30 % of the
maximum filling volume of the exposure bags and the exposure bags are moved
during the
irradiation with UV light so that the contents of the exposure bags are
circulated and zones
of changing layer thicknesses are formed by the movement wherein said UV light
used
comprises UVC radiation of less than 280 nm to 200 nm.
According to the present invention, the PCs are moved in a suitable manner in
their
exposure bags. The movement takes place here so vigorously that layers form in
areas
inside the PCs, these layers being so thin that they can be penetrated by the
UV radiation.
At the same time, the movement must be such that the PC suspensions are
efficiently
mixed in the bags. Both are to be realized when the following conditions
exist:
1. The exposure bags are highly flexible and they are not fixed during the
exposure,
e.g. clamped between quartz plates. They therefore adapt themselves to every
change
in form of the PC suspension, which occurs when the bags are moved.
2. The movement of the bags takes place either horizontally (linearly in a
back-and-
forth direction or in circular or ellipsoid shape) or else vertically
(rocked).
3. The exposure bags are filled to a maximum of 30 %, in particular to a
maximum of
20 % of their maximum filling volume.
In all cases, the reversal of the direction of movement is to be so abrupt
that the majority of
the PC suspension moves further into the original direction, as a result of
its inertia, and
therefore the residue which remains behind can form a thin layer which is
penetrable by
the UV radiation. In connection with the constant intermixing due to the
movement of the
bags during irradiation, finally the entire PC (and the viruses and/or
bacteria contained
therein) is exposed to the UV radiation. The PCs are thereby sterilised.
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The exposure bags are made from UV-transparent plastic material. Suitable
plastics are, for
example, ethylene vinyl acetate and polyolefins with sheet thicknesses of 1 mm
and less, in
particularly sheet thickness less than 0.5 mm. The exposure bags are
constructed so as to
be flat and preferably have no absorption maxima in the range of 200 to 320
nm. In the
horizontal filled state, the exposure bags are only a few mm thick, e.g. less
than 10 mm and
in particular less than 5 mm, preferably even less than 3 mm and they are
intended to hold
specimen volumes of for example up to 200 or up to 300 ml. The maximum holding
capacity (volume) of the exposure bag is, however, greater by at least factor
3, generally by
at least 5 times, preferably at least 10 or even at least 20 times greater
than the actual
specimen volume contained in it, which is to be treated.
Experimental Investigations
The described experiments illustrate the efficacy of the method and are not
limited to the
inactivation of the undermentioned bacteria and/or viruses. There is also no
limitation to
"random donor" PCs, which were used in the described experiments, and the
method
according to the invention is also able to be used on thrombapheresis
preparations. All the
experiments were carried out three to six times. The indicated results
represent in each case
the mean values standard deviation.
Platelet Concentrates
The PCs were produced from pools of respectively 5 buffy coats, which in turn
originated
from regular blood donations. The PCs had a volume of approximately 300 to 350
ml; the
platelet concentration was approximately 109/ml. The platelets were suspended
in storage
medium SSP+ (product of the company MacoPharma). The residual plasma content
was
approximately 30 to 40%.
Bacteriological Investigations
The following strains of bacteria were used in the inactivation experiments:
Staphylococcus (S.) epidermis
Staphylococcus (S.) aureus
Bacillus (B.) cereus
Klebsiella (K.) pneumoniae.
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Concentrations of bacteria were determined by means of a colony formation
assay and are
expressed as colony forming units (CFU)/ml. In the experiments for
inactivation of
bacteria, complete PCs or PC aliquots were spiked with 104 to 105 CFU/ml of
one of the
indicated species and then irradiated with UV light.
Virological Investigations
PC aliquots were spiked with suid herpes virus (SHV-1, pseudorabies virus,
Aujeszky
strain) or vesicular stomatitis virus (VSV, Indiana strain). Virus titers were
determined by
means of CPE assay (CPE = cytopathic effect). They are indicated as TCID50
(TCID =
tissue culture infective dose). Vero cells served as indicator cells. The
initial virus
concentration in the experiments which were carried out was approximately 105
to 107
TCID50.
Exposure Apparatus
One of the two exposure apparatus used was equipped with tubes which emitted
UVB
light. The irradiation took place from both sides of the exposure bags which
were put in
place, i.e. from above and from below. The exposure apparatus was provided
with a
shaking device which carried out back-and-forth movements at a frequency of 60
changes
of direction/min. A second exposure apparatus was likewise equipped with tubes
which
emitted UVB light. The irradiation likewise took place from both sides. A
third apparatus
(of the same type of construction as the second) was provided with tubes which
emitted
UVC light (wavelength: 254 nm). Both apparatus were able to be provided with 2
different
shaking devices: one horizontal shaker, which carried out ellipsoid back-and-
forth
movements, and a rocking shaker.
Exposure Bags
The exposure bags which were used consisted of ethylene vinyl acetate (EVA),
which is
penetrable by UV light. Two sizes of bags were used:
1. 14.5 x 18.5 cm (external bag area approx. 268 cm2)
2. 22.5 x 38 cm (external bag area approx. 855 cm2)
In the experiments with the small EVA bags, the sample volume was 80 ml, in
those with
the large bags approximately 300-350 ml (complete PCs were treated).
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Experiment Example 1:
Inactivation of S.epidermidis by UVB, with and without free movement of the
platelet
suspension during shaking
In the experiment, the sample volume was 80 ml. The free mobility of the
platelet
suspension during shaking, and hence the formation of a thin layer was
prevented in a
sample in that the exposure bags were clamped securely between two quartz
plates. The
resulting layer thickness was approximately 3 mm. In the second sample, the
distance
between the quartz plates was increased such that the platelet suspension was
largely able
to move freely during shaking. The two samples were irradiated with 1 J/cm2.
As Table 1 shows, the bacteria titer in the fixed samples was reduced by
approximately 2
log10, but by more than 4 logio in the loosely placed ones.
Table 1
Sample title Bacteria titer(logioCFU/m1)
Untreated control 4.1 0.03
Securely clamped sample 1.4 1.29
Loosely placed sample -0 .40 0.35
Experiment Example 2:
Inactivation of S.epidermidis by UVB in complete PCs, loosely or securely
clamped
exposure bags, with shaking
The PC volume in this experiment was 330 ml, the average layer thickness in
large EVA
bags was accordingly approximately 3.9 r-im. The PCs were irradiated with 3
UVB doses
(0.8, 1.0 and 1.2 J/cm2) under the following conditions:
1. without shaking, loosely placed between quartz plates
2. with shaking, pressed between quartz plates.
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As the experiment results show (Table 2), in the PCs which were securely
clamped during
shaking, the bacteria titer was reduced by the UVB treatment by up to
approximately 2
logio, by comparison in the loosely placed samples, depending on the dose, by
approximately 3.4 to more than 4 logio.
Table 2
Sample placement UVB Dose(J/cm2) Bacteria Titer
(logioCFU/m1)
shaken, securely clamped 0 4.11 0.00
shaken, securely clamped 0.8 2.14 0.48
shaken, securely clamped 1.0 1.95 0.03
shaken, securely clamped 1.2 1.99 0.03
shaken, loose 0 4.19 0.11
shaken, loose 0.8 0.77 0.69
shaken, loose 1.0 -0.14 0.05
shaken, loose 1.2 -0.40 0.05
Experiment Example 3:
Inactivation of further bacteria in freely movable or fixed PC aliquots by UVB
It can be seen from the first two experiment examples that S.epidermidis is
effectively
inactivated in PCs under the condition that the PC suspension can move freely
during the
UV irradiation. In the following experiment, the following additional strains
of bacteria
were tested: S.aureus, B.cereus and K.pneumoniae.
The conditions were the same as described in Experiment Example 1. In all
three cases a
similar result as with S.epidermidis: in the loosely placed PC samples, the
bacteria were
inactivated by approximately 3.9 to 4.29 logio, whereas the titers in the
fixed samples were
only reduced by approximately 2 to 3.4 logio (Table 3).
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Table 3
Strain of Sample Title Bacteria Titer
bacteria (logioCFU/m1)
S.aureus untreated control 4.88+0.00
S.aureus securely clamped, shaken 1.49+1.30
S.aureus loosely placed, shaken 0.97 0.86
B.cereus untreated control 4.99 0.09
B.cereus securely clamped, shaken 2.99 0.13
B.cereus loosely placed, shaken 0.74 0.68
K.pneumoniae untreated control 4.94 0.08
K.pneumoniae securely clamped, shaken 2.34 0.24
K.pneumoniae loosely placed, shaken 1.00 0.89
Experiment Example 4:
Inactivation of S.epidermidis in PC aliquots by UVB under various shaking
conditions
An investigation was carried out as to whether the inactivation of
S.epidermidis in loosely
placed PC aliquots is also increased when different horizontal shakers are
used from the
one used in Experiments 1 to 3, which, as mentioned, makes back-and-forth
movements. In
the following experiments, an orbital shaker was used which carried out a
circular
movement (radius: 3 cm, rotation rate: 50/min), in addition a rocker with 50
up- and down
movements per minute. Again, one of the two samples (80 ml) was clamped
securely
between quartz plates, the other was placed loosely. As can be seen from the
results shown
in Table 4, this time the extent of the bacteria inactivation was higher by 3
to 4 logio in the
loosely placed PC samples than in the securely clamped ones.
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Table 4
Shaker Sample Title Bacteria Titer
(log 0CFU/m1)
untreated control 4.94 0.16
Orbital securely clamped 4.23 0.00
Orbital loosely placed 0.50 0.39
Rocker securely clamped 4.02 0.17
Rocker loosely placed 0.87 0.78
Experiment Example 5:
Inactivation of suid herpes viruses by UVB, without or with free movement of
the PC
aliquots during shaking
In order to test whether the increase of inactivation of pathogens in PCs
which are not
fixed during irradiation with UV light, relates not only to bacteria but also
to viruses, the
following experiment was carried out: PC aliquots of 80 ml were spiked with
suid herpes
viruses (SHV-1) and were treated with UVB as described in Experiment Example
1. In the
freely placed samples, the virus titer was reduced by almost 4 logio, in the
securely
clamped samples, on the other hand, only by approximately 3 logio. This
confirms that
under the said conditions, the inactivation of viruses is also distinctly
improved.
Table 5
Sample Title Virus Titer (LogioTCID501
untreated control 4.4 0.2
securely clamped sample 1.41 0.18
loosely placed sample 0.56 0.15
Experiment Example 6:
Inactivation of vesicular stomatitis viruses by UVB, without or with free
movement of the
PC aliquots during shaking
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The experiment was carried out as described in Experiment Example 5, except
that the PC
aliquots were spiked with VSV instead of with SHV-1. Again, the extent of the
virus
inactivation in the loosely placed samples was greater by more than 6.46 logio
than in the
comparative samples, which were fixed between quartz plates during exposure
(Table 6). It
is, in fact, noticeable that also in these, the virus titer was relatively
greatly reduced (by
approximately 5.4 logio). VSV is clearly more UV-sensitive than SHV-1.
Table 6
Sample Title Virus Titer (LogioTCID50)
untreated control 6.7 1.05
securely clamped sample 1 .29 1 .05
loosely placed sample <0.24 0.00
Experiment Example 7:
Inactivation of S.epidermidis by UVC, without or with free movement of the PC
aliquots
during shaking
In this experiment, the irradiation took place with UVC instead of UVB. The UV
dose was
0.3 J/cm2 (exposure time: 60 sec). Otherwise, the conditions were as described
in
Experiment Example 1. As can be seen from Table 7, the bacteria titer in the
fixed samples
was only reduced by approximately 1 logio. This clearly reflects the small
penetration
depth of UVC into the platelet suspension. In the loosely placed samples, on
the other
hand, no more bacteria were able to be found; the inactivation factor was
greater than 4
logio.
Table 7
Sample Title Bacteria Titer (logioCFU/m1)
untreated control 4.08 0.04
securely clamped sample 2.99 0.13
loosely placed sample <0.24
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Experiment Example 8:
Inactivation of VSV by UVC, without or with free movement of the PC aliquots
during
shaking
As in Experiment Example 6, VSV was used as the test virus. The conditions
were the
same as in Experiment Example 7. The results shown in Table 8 show that also
in this
case, the extent of pathogen inactivation was much more marked in the loosely
placed
samples than in the fixed ones: whereas the virus titer in the latter was only
reduced by
approximately 1.5 logio it was approximately 6.2 logo in the non-fixed
samples.
Table 8
Sample Title Virus Titer (Log10TCID50)
untreated control 6.92 0.22
securely clamped sample 5 .47 0 .21
loosely placed sample 0.74 0.76
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